content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.observable.internal.operators;
  
  import java.util.concurrent.Callable;
  
  import io.reactivex.common.RxJavaCommonPlugins;
  import io.reactivex.common.exceptions.Exceptions;
  import io.reactivex.common.internal.functions.ObjectHelper;
  import io.reactivex.observable.*;
  import io.reactivex.observable.internal.observers.DeferredScalarDisposable;
  
  /**
   * Calls a Callable and emits its resulting single value or signals its exception.
   * @param <T> the value type
   */
  public final class ObservableFromCallable<T> extends Observable<T> implements Callable<T> {
      final Callable<? extends T> callable;
      public ObservableFromCallable(Callable<? extends T> callable) {
          this.callable = callable;
      }
      @Override
      public void subscribeActual(Observer<? super T> s) {
          DeferredScalarDisposable<T> d = new DeferredScalarDisposable<T>(s);
          s.onSubscribe(d);
          if (d.isDisposed()) {
              return;
          }
          T value;
          try {
              value = ObjectHelper.requireNonNull(callable.call(), "Callable returned null");
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              if (!d.isDisposed()) {
                  s.onError(e);
              } else {
                  RxJavaCommonPlugins.onError(e);
              }
              return;
          }
          d.complete(value);
      }
  
      @Override
      public T call() throws Exception {
          return callable.call();
      }
  }
  